Teller protection units are well known. A typical teller protection unit has a frame with a piece of bullet-proof or bullet-resistant glass mounted therein. The frame is mounted in a wall. A teller or other person having valuables to be protected, stands on one side of the teller protection unit and customers stand on the other side. The teller and the customers pass articles or valuables back and forth, typically through a deal tray which is a part of the teller protection unit. Communication between tellers and customers is sometimes difficult because the bullet-resistant glass is a laminated glass, having a thickness on the order of several centimeters. The laminated glass is usually flush-mounted with a frame or with extensive supporting members in the frame. As a result, sound can only be effectively communicated through the deal tray which is the only open portion of the teller protection unit. This is an inconvenience for both the teller and the customers because, often, it forces both parties to stoop close to the tray in order to be heard.
Some teller protection units are manufactured with one or more voice transmission boxes positioned near a bottom of the teller protection unit. These voice transmission boxes aid somewhat in transmitting sound from one side of the teller protection unit to the other. However, a person who is trying to hear the person on the opposite side must direct his attention downward and this is an inconvenience. It may be appreciated that when a person's attention is directed downward, for instance, while money is being counted, it is difficult for the person to hear the teller making the count and watch the teller at the same time. As a result, the voice transmission units which are mounted in the bottom of the teller protection unit, offer only a small improvement over acoustical transmission through the tray.
One method has been found for solving this problem, which uses electronics. Microphones are positioned on both sides of the teller protection unit, as are loudspeakers. An amplifier links both sets of microphones and loudspeakers. This system does offer the advantages of clear speech and amplification, but it requires that both parties stay close to their respective microphones so that fading of the signal does not occur and understanding can be clear between both of the parties. In addition, an electronic intercom system of the type described is usually expensive.
What is needed then, is an acoustical transmission system for a teller protection unit which provides uniform balanced acoustical transmission between a major portion of the frame, and the bullet-resistant glass of the teller protection unit. Furthermore, this acoustical transmission system should not detract from the safety which the teller protection unit provides.